Apparatus for settling insulation material in cryogenic tanks

ABSTRACT

The apparatus comprises a vibrator and a device for anchoring the vibrator to surface of tank wall in such a manner that the bond between the surface-anchoring device and the tank wall surface is releasable. The surface-anchoring device includes either an electromagnet or a permanent magnet, or a vacuum cup. Release is obtained by deenergizing the electromagnet, or by releasing the vacuum. Cams mounted adjacent the permanent magnet bear against the tank wall and force the pole pieces away from the tank wall to release the magnetic bond. The tank wall vibrates over a considerable area and the vibrations are transmitted to the insulation material to settle same. A rope supports the apparatus when the surface bond is released so that it can be shifted to a different wall portion.

United States Patent [72] Inventor Carl Mendius, Jr.

Naperville, Ill.

[21] Appl. No. 866,268

[22] Filed Oct. 14, 1969 [45] Patented Jan. 11, 1972 [73] Assignee Silbrico Corporation Hodgkins, Ill.

Continuation-in-part of application Ser. No. 774,000, Nov. 7, 1968. This application Oct. 14, 1969, Ser. No. 866,268

[54] APPARATUS FOR SETTLING INSULATION MATERIAL IN CRYOGENIC TANKS 11 Claims, 5 Drawing Figs.

Primary Examiner-Robert W. Jenkins Attorney-Zabel, Baker, York and Jones ABSTRACT: The apparatus comprises a vibrator and a device for anchoring the vibrator to surface of tank wall in such a manner that the bond between the surface-anchoring device and the tank wall surface is releasable. The surface-anchoring device includes either an electromagnetor a permanent magnet, or a vacuum cup. Release is obtained by deenergizing the electromagnet, or by releasing the vacuum. Cams mounted adjacent the permanent magnet bear against the tank wall and force the pole pieces away from the tank wall to release the magnetic bond. The tank wall vibrates over a considerable area and the vibrations are transmitted to the insulation material to settle same.'A rope supports the apparatus when the surface bond is released so that it can be shifted to a different wall portion.

SHEET 1 [IF 2 INVENTOR CARL MEND/US, JR.

PATENTED JAN! 1 [972 SHEET 2 OF 2 APPARATUS FOR SETTLING INSULATION MATERIAL IN CRYOGENIC TANKS This application is a continuation-in-part of my copending application, Ser. No. 774,000 filed Nov. 7, 1968.

This invention relates to apparatus for settling the insulating material in vessels used for the storage of low-temperature liquids.

When the'boiling point of the product to be stored is very low, such tanks are referred to as cryogenic tanks. This term is used herein interchangeably with low-temperature liquid storage tank, since the principles of my invention are applicable to insulated tanks irrespective of the specific boiling point of the product to be stored.

Such low-temperature liquid storage tanks are doublewalled vessels of substantial size. For example, a tank may have a diameter of 150 feet and a height of 100 feet to the rim. The double wall provides a cavity which may have a width of from 2 to feet, depending on the product stored. This cavity is filled with suitable insulation, such as perlite. The term perlite as used herein, refers to perlite in its expanded form which provides a lightweight effective insulating material having satisfactory flow characteristics.

In one type of low-temperature liquid storage tank the double wall construction includes the roof of the tank. As the insulation settles over a period of months the perlite in the domed double wall of the roof serves as a reservoir so the sidewall cavity is maintained full.

However, in certain types of tank construction, the roof is not insulated in this manner. In one type, the inner wall is open at the top, and in another type, it is extended up to the roof. Here it has been found that the settlement of the perlite, which represents a 5 to 12 percent shrinkage, will leave the upper portion of the wall cavity uninsulated. Therefore after a period of time, it is necessary to open up the tank and put additional insulation in the top of the wall cavity, referred to as topping off." However, once the tank has been charged with the liquid to be stored, this subsequent topping off operation is not practical with the result that the cost advantages of the open inner wall type, for example, are not available unless one is willing to delay the charging of the tank, or else is willing to sacrifice the 5 to 12 percent storage capacity represented by the settling of the insulation.

Although it has been proposed to settle the insulation in various double wall structures, such as refrigerators, by vibration, to my knowledge it has not been previously proposed to apply such techniques to very large structures such as lowtemperature liquid storage tanks.

According to my invention, vibrations are induced in only a portion of the tank wall. I have found that the wall vibrations will be transmitted to the insulating material adjustment thereto in such a manner that the insulation material will be settled throughout its entire thickness of from 2 to 5 feet. Thus, by shifting the location of the vibration-inducing means from place to place until substantially all portions of the tank wall have been vibrated, it is possible to settle all of the insulation material.

The settling operation can be performed either sequentially, that is, after the entire cavity has been initially filled, or concurrently with the filling.

l have found that a wall portion of substantial area can be vibrated by firmly securing a vibrator to the outer wall or skin of the tank. The vibrator thus acts as the driver of a diaphragm, that part of the tank wall located within a certain radius of the vibrator constituting the diaphragm. The effective radius of the vibrating wall portion will depend upon the power of the vibrator; for purposes of discussion it can be assumed to be feet. Therefore, when a larger wall portion is to be vibrated, a number of vibrators may be used, spaced from each other by 30 feet.

In my initial experimentation, I anchored the vibrators to the skin of the tank by mechanical interlocking means. A number of brackets were first welded to the skin. Then the vibrators were bolted to the brackets. Two vibrators were used, the vibrators being shifted every few hours.

One disadvantage of this procedure is the expense of welding the brackets in place, and them removing them and grinding off the weld spots. Also the tank at each weld spot should be checked after grinding, by Magnaflux techniques. for defects or other damage caused by the welding and cutting operations. Furthermore, scaffolding is required for the welding operation, for bolting and unbolting the vibrators, and for removing the brackets. Also the use of fixed vibrator locations doesnot lend itself to some settling methods in which there must be considerable latitude in the location of the vibrators due to variations in' the location and size of the different piles of insulation being deposited.

I have now found that the vibrator can be secured to the wall of the tank by means which do not disturb the molecular or grain structure of the wall, but which nevertheless is sufficiently secure that the vibrating action of the vibrator does not result in any creeping of the mechanism. Such means I refer to herein as a surface-anchoring device because the anchoring action is in the form ofa bond to the surface of the tank wall.

An important feature of my invention is that the surface bond is one that can be released so that the settling unit as a whole may be shifted from one portion of the wall to another. Preferably the release of the bond is remotely controlled. A rope or the like supports the settling unit when the bond is released.

The output portion of the vibrator or the like is referred to as the impact plate, and this is generally bolted or welded to the object to be vibrated. In providing a releasable surface bond according to my invention, a principal requirement is that the surface of the impact plate of the settler be maintained in contact with the surface of the tank wall with a force sufficiently great that all of the vibratory motion will be transmitted to the tank wall. lnsufficient force will cause energy loss through sliding friction and impact, resulting in adequate settling, and will reduce the effective diaphragm area, and may cause hammering which could damage the tank structure.

Present practice indicates that adequate settling should result in a 12 percent reduction of the original volume of the perlite.

The use of my invention provides a very substantial savings in labor and time as compared with my initial proposal which involved first the welding and then the removal of brackets. In a tank of the size indicated, this alone represents a saving of from 2 to 4 days of time.

Other objects, features and advantages will become apparent as the description proceeds. In the drawings:

FIG. 1 is a sectional elevation ofa preferred embodiment of my invention;

FIG. 2 is a vertical section through a tank illustrating the operation of the settling unit of FIG. 1;

FIG. 3 is a side elevation of a modified settler unit;

FIG. 4 is a front elevation of FIG. 3; and

FIG. 5 is a side elevation, partly in section, showing a further modification.

FIG. 2 shows a tank 10 of the open inner wall type having an outer wall or skin 11 which is erected on a foundation 12. A domed roof 13 is provided for the skin 12. A suitable manhole or other opening in the roof is provided, represented herein by the collar 14. The tank also includes an open inner wall 15 which is secured to the foundation 12. A layer of suitable insulation l6 and a steel'bottom l9 overlie the foundation l2, and form the bottom of the inner tank. Between the outer wall 11 and the inner wall 15 is a wall cavity 17 in which the insulation 18 is located.

The outer wall or skin 11 is formed of steel plates, such as quarter-inch steel plates, and together with the roof 13 constitutes a self reinforcing structure. A suitable work floor 20 may be located at the top of the inner wall and may also serve to support a layer of insulation, not shown. The work floor 20 as shown, is suspended by rods 21 from the roof 13.

The insulation 18 is deposited in the cavity 17 by a flexible conduit 22 which extends from suitable perlite expanding and conveying equipment, not shown, through the manhole collar 14, with its end extending into the upper part of the cavity 17.

As the insulation material drops out of the end of the conduit, the material is deposited in a pile, and the location of the conduit'22 is shifted from time to time to distribute the piles around the periphery of the tank.

The settler unit 25, shown in FIGS. 1 and 2, comprises a surface-anchoring device 26 and a vibrator 27 which is mounted thereon in vibration-transmitting relationship.

The surface-anchoring device 26 is of an electromagnetic type comprising a core structure 45 and a direct current energizing winding 47. Any one of several electromagnetic constructions is suitable, the FIG. I construction being illustrative only. In the arrangement shown, the core structure is of cylindrical shape and has an annular recess in its circular front surface in which the energizing winding 47 is disposed. The front surface thus comprises the two concentric pole pieces of a pot-type core. In this arrangement the pole pieces constitute the impact plate 46 for transmitting vibrations to the tank wall 11.

A cable 42 leads from the winding 47 to a remotely located control box which contains a control switch 43 and a suitable rectifier.

The vibrator 27 is shown diagrammatically as an air driven vibrator but other types of vibrators will perform equally well, such as an electrically driven eccentric vibrator, a ball-type vibrator, or a magnetic vibrator. It has been found that a Navco air-driven vibrator No. BH 3" short, silent type, operates satisfactorily. Since this particular vibrator is preferably mounted at an angle to the horizontal, the core structure 45 carries on its rear surface a suitable mount 48 for the vibrator 27. The vibrator 27 includes an integral impact plate 29 which is bolted to the mount 48.

A flexible airhose 40 connects the vibrator 27 with a compressor 41 located on the ground.

The settling unit has a support lug 30 through which a rope 31 is threaded and knotted. The rope is supported by a wheeled scaffold support 33 at the top of the tank 10 comprising a rod 34 having a rubber-tired wheel 35 mounted thereon by suitable bearings. A cable 36 connects the inner end of the rod 34 to the roof collar 14. A pulley 37 is carried at the outer end of the rod 34. The rope 31 is trained over the pulley 37, and its outer end is secured to the drum of a winch 38. The wheeled scaffold support 33 is of particular utility because of the ease with which the settling unit 25 may be shifted either vertically or laterally. Although only one settling unit 25 is shown in FIG. 2, it is contemplated that a plurality of laterally spaced settling units be used simultaneously, and in this event, a separate scaffold support 33 is provided for each.

In the FIG. 1 arrangement the bond between the surface anchoring device 26 and the surface of the skin 11, is a magnetic bond. The advantage of the magnetic bond is that the settling unit is bonded to the skin surface at the impact plate 46. A further advantage is that the bond is easily releasable, merely by deenergizing the winding 47 by opening the control switch 43 remotely located at the base of the tank.

A magnetic bond can also be provided by permanent magnets 50, as shown in FIGS. 3 and 4. Here the surface-anchoring device 26a comprises a body portion 51 in the form of a block of nonmagnetic material formed with two recesses 52 in its front surface, the recesses opening also into one side surface. The permanent magnets 50 are received in the recesses 52 and secured thereto by bolts 53. The front or pole pieces 54 of the magnets 50 constitute the impact plate, and project slightly beyond the block 51. The magnetic bond is released by means of eccentric cams 55 located adjacent the sidewalls of the block 51, as shown in FIG. 4. The cams 55 rotate on shafts 56 which extend through and are journaled in the block 51, there being two cams on each shaft. Each pair of cams is operated by a single operating arm 58 having an eye at the outer end for a suitable pull rope, not shown. Thus, when the operating arm 58 is pulled downwardly, the block 51 will be cammed away from the tank wall 11, breaking the bond between the impact plate 54 and the surface of the wall 11. A torsion spring 57 is provided for each shaft to cause the cams to return to the retracted position of FIG. 3. Both operating arms 58 can be operated by a single rope, and the release of the magnetic bond can be controlled by an operator at the base of the tank.

The block 51 also provides a mount 59 for the vibrator 27. Thus the vibrations are transmitted from the vibrator 27 through the block 51 and the magnets 50 to the tank wall II, the magnet surfaces 54 constituting the impact plate. An advantage of this arrangement is that it requires no electric circuit, and is not affected by power failure.

FIG. 5 shows a surface-anchoring device 26h suitable for use on stainless steel or aluminum tank walls. Here the bond is a vacuum bond created by suction means. The body ofthe surface-anchoring device 26h comprises a body member 60 having a mount 61 to which is secured the vibrator 27. The front surface 62 of the body member comprises the impact plate which is urged into contact with the tank wall 11. An annular chamber 63 surrounds the body member 60 and has at its front edge a flexible sealing flange 64, such as a rubber flange. When the air is evacuated from the chamber 63 through a flexible suction line 65, the impact plate 62 will be pressed into engagement with the tank wall 11 in vibration-transmitting relationship. The friction between the impact plate 62 and the surface of the tank wall 11 is sufficient under the pressures involved to transmit all of the vibratory motion and to maintain the settling unit in position. The diameter of the chamber 63 and the degree of vacuum within the chamber, determine the magnitude of the frictional force developed. The vacuum bond provided by the arrangement shown is released by venting the chamber 63 to the atmosphere 67 through a suitable two-way valve 66 in the suction line 65. The valve 66 can be located remotely from the device 26b, preferably at the base of the tank to provide a remote control for the release.

In one installation, the double-walled tank was about ll5 feet in diameter and 94 feet high, and the wall cavity was 4 feet thick. The wall cavity was filled up to the top of the inner wall, and then six settling units were applied to the outer wall of the tank. These settling units had an electromagnetic surface-anchoring device 26 as shown in FIG. I, the electromagnet initially drawing 350 watts.

The horizontal spacing was 30 feet and initially they were located 15 feet above the base of the tank. They were operated for approximately 3 hours and then elevated 30 feet and operated for 3 hours at that level and then elevated 30 feet more and operated for 3 hours at the third level. The six vibrators extended over one-half of the tank circumference. Then they were moved to the other side of the tank and operated at each of the three levels for approximately 3 hours each. It was found that the perlite had settled approximately 12 percent from its original volume. Then the empty space at the top was filled and the tank wall was again vibrated at the third level. After this'vibration had been completed, additional perlite was added to bring the level up to the top of the inner wall.

The invention is also applicable in settling tanks in which the double wall construction includes the roof of the tank. Also, the vibrators can be spaced vertically rather than horizontally, and after each vertical section of the tank has been vibrated, the several vibrators can be shifted horizontally to a new location until the entire circumference of the tank has been subjected to vibration.

The subject matter of the aforesaid copending application Ser. No. 774,000 is incorporated herein by reference, insofar as consistent with the present disclosure.

Although only preferred embodiments of the present invention have been described herein, it will be understood that various modifications and changes may be made in the constructions shown without departing from the scope of the invention, as pointed out in the appended claims.

Iclaim:

1. In combination, a low-temperature liquid storage tank having inner and outer walls providing a wall cavity, insulation material disposed in said cavity, vibrator means, permanent magnet means to anchor said vibrator means to the surface of one of said walls in vibration transmitting contact therewith to cause a portion of said tank wall to vibrate over a substantial area, the vibration of said tank wall portion being transmitted to the insulation material contacting the opposite surface of said vibrating wall portion to settle same, and means for forcing said permanent magnet means away from said wall surface to break the magnetic bond therebetween.

2. In combination, a low-temperature liquid storage tank having inner and outer walls providing a wall cavity, insulation material disposed insaid cavity, vibrator means, vacuum means to anchor said vibrator means to the surface of one of said walls in vibration-transmitting contact therewith to cause a portion of said tank wall to vibrate over a substantial area, the vibration of said tank wall portion being transmitted to the insulation material contacting the opposite surface of said vibrating wall portion to settle same, and means to release the vacuum within said vacuum means so that said vibrator means can be shifted to a different wall portion.

3. In combination, a low-temperature liquid storage tank having inner and outer walls providing a wall cavity, insulation perlite material disposed in said cavity, vibrator means, means anchoring said vibrator means to the surface of one of said walls in vibration-transmitting contact therewith to cause only a portion of said tank wall to vibrate over a substantial area, the vibration of said tank wall portion being transmitted to the insulation material contacting the opposite surface of said vibrating wall area to settle same.

4. The combination as claimed in claim 3 which includes means to render said anchoring means inoperative, means for supporting said vibrator means when said anchoring means is inoperative, said supporting means being shiftable with respect to said tank so that the location of said vibrator means can be shiftedv 5. The combination as claimed in claim 3 in which said outer tank wall is a steel wall, said anchoring means comprising an electromagnet.

6. Settling apparatus for perlite insulation material contained in the wall cavity of a low-temperature liquid storage tank comprising a settling unit having anchoring means operative to form a releasable bond with the surface ofa wall of said tank, a vibrator mounted on said anchoring means, said settling unit having a surface contacting said tank wall for transmitting the vibrations from said vibrator to only a portion of the wall of said tank to cause the same to vibrate over a substantial area, the vibration of said tank wall portion being transmitted to the insulation material contacting the opposite surface of said vibrating wall area to settle same.

7. Settling apparatus as claimed in claim 6 which includes supporting means for supporting said settling unit with respect to said tank when said anchoring means is inoperative, said supporting means being shiftable with respect to said tank so that the location ofsaid settling unit can be shifted.

8. Settling apparatus as claimed in claim 6 in which said anchoring means comprises an electromagnet.

9. Apparatus for settling insulation material contained in the wall cavity of a low-temperature liquid storage tank comprising a surfaceanchoring device including an impact plate, a vibrator mounted on said surface-anchoring device, said surface-anchoring device being operative to create a releasable magnetic surface bond between said device and the surface of a wall of said tank, and said su rface-anchoring device developing a sufficient force between said impact plate and the surface of said wall so that all of the vibratory motion of said apparatus will be transmitted to the portion of said tank wall contacted bysaid impact plate to cause said tank wall to vibrate over a substantial area, the vibration of said tank wall portion being transmitted to the insulation material contacting the opposite surface of said vibrating area to settle same, said surface-anchoring device including a permanent magnet having a pole surface which constitutes said impact plate, and a body portion, said permanent magnet being mounted on said body portion, a cam mounted on said body portion for engagement with said wall surface for forcing said body portion and said magnet away from said wall surface to release said magnet bond, and remotely controlled means for rotating said cam.

10. Apparatus for settling insulation material contained in I the wall cavity ofa low-temperature liquid storage tank comprising a surface-anchoring device including an impact plate, a vibrator mounted on said surface-anchoring device, said surface-anchoring device being operative to create a releasable surface bond between said device and the surface of a wall of said tank, and said surface-anchoring device developing a sufficient force between said impact plate and the surface of said wall so that all of the vibratory motion of said apparatus will be transmitted to the portion of said tank wall contacted by said impact plate to cause said tank wall to vibrate over a substantial area, the vibration of said tank wall portion being transmitted to the insulation material contacting the opposite surface of said vibrating area to settle same, said surfaceanchoring device including a body member having a wall-contacting surface, said wall-contacting surface constituting said impact plate, a vacuum chamber mounted on said body por tion member adjacent to said impact plate and being open on that side which is coplanar with said impact plate and providing edges bounding said open side, a flexible sealing flange mounted on said edges for engagement with said wall surface, means for evacuating said vacuum chamber, and means for releasing the vacuum in said vacuum chamber so that said surface-anchoring device can be shifted to a different portion of said tank wall.

11. Apparatus for settling expanded perlite insulation contained in the wall cavity of a low-temperature liquid storage tank comprising a surface-anchoring device including an impact plate, a vibrator mounted on said surface anchoring device, said surface-anchoring device being anchored to a portion of a wall of said tank and including means creating a releasable surface bond between said impact plate and the surface of said tank wall, and said surface-anchoring device developing a sufficient force between said impact plate and the surface of said wall so that all of the vibratory motion of said apparatus will be transmitted to the portion of said tank wall contacted by said impact plate to cause said tank wall to vibrate over a substantial area, the vibration of said tank wall portion being transmitted to the insulation material contacting the opposite surface of said vibrating area to settle same, said surface-anchoring device including a permanent magnet having a pole surface which constitutes said impact plate, and a body portion, said permanent magnet being mounted on said body portion, said surface bond being a magnetic bond between said impact plate and said tank wall surface, and release means mounted on said body portion for engagement with said wall surface for forcing said body portion and said magnet away from said tank wall surface to release said magnetic bond. 

1. In combination, a low-temperature liquid storage tank having inner and outer walls providing a wall cavity, insulation material disposed in said cavity, vibrator means, permanent magnet means to anchor said vibrator means to the surface of one of said walls in vibration transmitting contact therewith to cause a portion of said tank wall to vibrate over a substantial area, the vibration of said tank wall portion being transmitted to the insulation material contacting the opposite surface of said vibrating wall portion to settle same, and means for forcing said permanent magnet means away from said wall surface to break the magnetic bond therebetween.
 2. In combination, a low-temperature liquid storage tank having inner and outer walls providing a wall cavity, insulation material disposed in said cavity, vibrator means, vacuum means to anchor said vibrator means to the surface of one of said walls in vibration-transmitting contact therewith to cause a portion of said tank wall to vibrate over a substantial area, the vibration of said tank wall portion being transmitted to the insulation material contacting the opposite surface of said vibrating wall portion to settle same, and means to release the vacuum within said vacuum means so that said vibrator means can be shifted to a different wall portion.
 3. In combination, a low-temperature liquid storage tank having inner and outer walls providing a wall cavity, insulation perlite material disposed in said cavity, vibrator means, means anchoring said vibrator means to the surface of one of said walls in vibratioN-transmitting contact therewith to cause only a portion of said tank wall to vibrate over a substantial area, the vibration of said tank wall portion being transmitted to the insulation material contacting the opposite surface of said vibrating wall area to settle same.
 4. The combination as claimed in claim 3 which includes means to render said anchoring means inoperative, means for supporting said vibrator means when said anchoring means is inoperative, said supporting means being shiftable with respect to said tank so that the location of said vibrator means can be shifted.
 5. The combination as claimed in claim 3 in which said outer tank wall is a steel wall, said anchoring means comprising an electromagnet.
 6. Settling apparatus for perlite insulation material contained in the wall cavity of a low-temperature liquid storage tank comprising a settling unit having anchoring means operative to form a releasable bond with the surface of a wall of said tank, a vibrator mounted on said anchoring means, said settling unit having a surface contacting said tank wall for transmitting the vibrations from said vibrator to only a portion of the wall of said tank to cause the same to vibrate over a substantial area, the vibration of said tank wall portion being transmitted to the insulation material contacting the opposite surface of said vibrating wall area to settle same.
 7. Settling apparatus as claimed in claim 6 which includes supporting means for supporting said settling unit with respect to said tank when said anchoring means is inoperative, said supporting means being shiftable with respect to said tank so that the location of said settling unit can be shifted.
 8. Settling apparatus as claimed in claim 6 in which said anchoring means comprises an electromagnet.
 9. Apparatus for settling insulation material contained in the wall cavity of a low-temperature liquid storage tank comprising a surface-anchoring device including an impact plate, a vibrator mounted on said surface-anchoring device, said surface-anchoring device being operative to create a releasable magnetic surface bond between said device and the surface of a wall of said tank, and said surface-anchoring device developing a sufficient force between said impact plate and the surface of said wall so that all of the vibratory motion of said apparatus will be transmitted to the portion of said tank wall contacted by said impact plate to cause said tank wall to vibrate over a substantial area, the vibration of said tank wall portion being transmitted to the insulation material contacting the opposite surface of said vibrating area to settle same, said surface-anchoring device including a permanent magnet having a pole surface which constitutes said impact plate, and a body portion, said permanent magnet being mounted on said body portion, a cam mounted on said body portion for engagement with said wall surface for forcing said body portion and said magnet away from said wall surface to release said magnet bond, and remotely controlled means for rotating said cam.
 10. Apparatus for settling insulation material contained in the wall cavity of a low-temperature liquid storage tank comprising a surface-anchoring device including an impact plate, a vibrator mounted on said surface-anchoring device, said surface-anchoring device being operative to create a releasable surface bond between said device and the surface of a wall of said tank, and said surface-anchoring device developing a sufficient force between said impact plate and the surface of said wall so that all of the vibratory motion of said apparatus will be transmitted to the portion of said tank wall contacted by said impact plate to cause said tank wall to vibrate over a substantial area, the vibration of said tank wall portion being transmitted to the insulation material contacting the opposite surface of said vibrating area to settle same, said surface-anchoring device including a body member having a wall-contacting surface, said wall-contaCting surface constituting said impact plate, a vacuum chamber mounted on said body portion member adjacent to said impact plate and being open on that side which is coplanar with said impact plate and providing edges bounding said open side, a flexible sealing flange mounted on said edges for engagement with said wall surface, means for evacuating said vacuum chamber, and means for releasing the vacuum in said vacuum chamber so that said surface-anchoring device can be shifted to a different portion of said tank wall.
 11. Apparatus for settling expanded perlite insulation contained in the wall cavity of a low-temperature liquid storage tank comprising a surface-anchoring device including an impact plate, a vibrator mounted on said surface anchoring device, said surface-anchoring device being anchored to a portion of a wall of said tank and including means creating a releasable surface bond between said impact plate and the surface of said tank wall, and said surface-anchoring device developing a sufficient force between said impact plate and the surface of said wall so that all of the vibratory motion of said apparatus will be transmitted to the portion of said tank wall contacted by said impact plate to cause said tank wall to vibrate over a substantial area, the vibration of said tank wall portion being transmitted to the insulation material contacting the opposite surface of said vibrating area to settle same, said surface-anchoring device including a permanent magnet having a pole surface which constitutes said impact plate, and a body portion, said permanent magnet being mounted on said body portion, said surface bond being a magnetic bond between said impact plate and said tank wall surface, and release means mounted on said body portion for engagement with said wall surface for forcing said body portion and said magnet away from said tank wall surface to release said magnetic bond. 